Describe the circumstances under which Oedipus unknowingly kills his true father, Laius.

The oracle at Delphi tells the King and Queen of Thebes,
Laius and Jocasta, that their infant son will kill them.  So, they pinion his feet and
tell a shepherd to take him to the mountains to die.

The
shepherd takes pity on the baby, and he gives him to another shepherd from the nearby
city-state Corinth.  There, the King and Queen, who could not otherwise conceive a
child, welcome the boy as their own.

Once a teenager,
Oedipus (whose name means "swollen foot") is told by a peer that he is a bastard,
something he has been paranoid about for a while.  To confirm this, he visits the Oracle
at Delphi, which tells him he will kill his
father.

Thinking his father is in Corinth, he runs as far
away from that city-state as he can.  On the way to Thebes, he meets a man driving a
cart of slaves at a crossroads.  The man deals harshly with the teen, who is crippled
and walks with a cane.  The man tells him to move from the road.  Oedipus refuses, and
the two come to blows.  Oedipus strikes him dead with his
cane.

As he enters the city of Thebes, he answers the
Riddle of the Sphinx and frees the city from the plague.  Joyful, they crown him their
King, a position that has been vacant.  Oedipus must marry the sitting Queen,
Jocasta.

Little do any of them know that Jocasta is
Oedipus' mother and the man he killed at the crossroads is his father.  All this is the
antecedent action to the play Oedipus Rex.